1. Field of the Invention
This invention relates to an automotive air conditioner for conditioning air in a room of an automobile. The automotive air conditioner of the present invention is effectively applied to an automobile which does not have a surplus heat source as, for example, an electric automobile.
2. Related Art
Usually, an automotive air conditioner makes use, in order to heat air, of heat from cooling water for an engine for driving an automobile. However, heating of air is performed using a heat pump when the amount of heat of cooling water for an engine is insufficient or when an automobile does not originally have engine cooling water such as an electric automobile.
For example, in an automotive air application Ser. No. 60-219114, a flow of refrigerant is changed over by means of a four-way valve such that an inside heat exchanger is used either as an evaporator to cool air or as a condenser to heat air.
With the automotive air conditioner wherein cooling operation and heating operation are performed alternatively by changing over of a four-way valve in this manner, since the single heat exchanger changes its function immediately between a function of an evaporator and another function of a condenser, there is the possibility that, particularly when the function is changed over, a large amount of moisture may be blasted from a surface of the inside heat exchanger toward the inside of the room of the automobile.
In particular, water condensed on a surface of the inside heat exchanger during cooling operation is evaporated from the surface of the inside heat exchanger as a result of changing over to heating operation and then carried into the room of the automobile by a blower. Such blasting of a large amount of water will instantaneously fog a windshield and/or window glass. The fog will make an obstacle to a field of view in driving the automobile and is very inconvenient.
Accumulator cycles are conventionally known wherein a subcooling control valve is disposed on the downstream side of a refrigerant condenser to obtain a subcooled condition of refrigerant.
An exemplary one of subcooling control valves is disclosed, for example, in Japanese Utility Model Laid-Open Application No. Showa 55-85671 and is shown in FIG. 100. Referring to FIG. 100, the subcooling control valve 1100 includes a valve body 1103 for opening or closing a throttle section 1102 by operation of a diaphragm 1101, a regulating spring 1104 for normally biasing the valve body 1103 to open the throttle section 1102, and a temperature sensitive tube 1105 for converting a variation of temperature of refrigerant on the downstream side of a refrigerant condenser (not shown) into a variation of pressure.
The displacement of the valve body 1103 is adjusted by the balance between the pressure in the temperature sensitive tube 1105 which acts upon the upper side of the diaphragm 1101 via a capillary tube 1106 and the high pressure of the refrigerant and the biasing force of the regulating spring 1104 which both act upon the lower side of the diaphragm 1101, and the opening of the throttle section 1102 depends upon the displacement of the valve body 1103.
However, in the subcooling control valve 1100 described above, since the biasing force of the regulating spring 1104 is set in advance so that a predetermined subcooling degree (for example, 5 to 10xc2x0 C.) may be obtained within the refrigerant condenser, when it is tried to construct such a novel subcooling cycle as shown in FIG. 101 or 1017 using the subcooling control valve 1100, such subjects to be solved as described below are involved.
Referring first to FIG. 101, the subcooling cycle shown constitutes a heat pump cycle for an automotive air conditioner and includes a refrigerant compressor 1200, an interior condenser 1202 disposed in a duct 1201 which introduces blast air into the room of the automobile, a subcooling control valve 1100, an interior evaporator 1203 disposed in the duct 1201 on the upstream side of the interior condenser 1202, an evaporation pressure regulating valve 1204, an exterior evaporator 1205 disposed on the outside of the duct 1201, an accumulator 1206, a bypass passageway 1207 for bypassing the interior evaporator 1203 and the evaporation pressure regulating valve 1204, and a solenoid valve 1208 for opening or closing the bypass passageway 1207.
Now, if the bypass passageway 1207 is closed by the solenoid valve 1208 so that the refrigerant flowing out through the subcooling control valve 1100 is introduced into the interior evaporator 1203, then air introduced into the duct 1201 by a fan 1209 is cooled when it passes through the interior evaporator 1203, and thereafter, the air is heated when it passes through the interior condenser 1202, and then it blown out into the room of the vehicle. In this instance, when the saturation temperature of the refrigerant flowing through the interior condenser 1202 is 50xc2x0 C. or around it, as cool air of a temperature close to 0xc2x0 C. cooled by the interior evaporator 1203 is blown to the interior condenser 1202, ideally a subcooling degree of the temperature of 50xc2x0 C. or so can be obtained at the interior condenser 1202.
On the other hand, if the bypass passageway 1207 is opened by the solenoid valve 1208 to allow the refrigerant flowing out from the subcooling control valve 1100 to be introduced into the exterior evaporator 1205 while an internal air mode is set so that air in the automobile room of a temperature of 30xc2x0 C. or around it is introduced into the duct 1201, then the air introduced in the duct 1201 is blown to the interior condenser 1202 while keeping its temperature (30xc2x0 C.) without being cooled by the interior evaporator 1203. Consequently, only a subcooling degree of the temperature of 20xc2x0 C. or so to the utmost can be obtained at the interior condenser 1202.
In the meantime, the subcooling cycle shown in FIG. 102 constitutes a refrigerating cycle for an automotive air conditioner and includes an exterior evaporator 1210 on the upstream side of an interior condenser 1202, and an air mixing damper 1211 for adjusting the amount of draft air to the interior condenser 1202. When the air mixing damper 1211 is opened or closed, cooling air of the temperature of 0xc2x0 C. or around it cooled by an interior evaporator 1203 is blown to or not blown to the interior condenser 1202.
For example, when the air mixing damper 1211 fully opens the interior condenser 1202 (the position indicated by full lines in FIG. 102) so that cool air of the temperature of 0xc2x0 C. or around it is blown to the interior condenser, if the saturation temperature of the refrigerant flowing through the interior condenser 1202 is 50xc2x0 C. or around it, a subcooling degree of the temperature ideally of 50xc2x0 C. or around it can be obtained.
On the other hand, when the air mixing damper 1211 closes the interior condenser 1202 (the position indicated by chain lines in FIG. 102), cool air is not blown to the interior condenser 1202, and the interior condenser 1202 acts as a mere refrigerant passageway. Consequently, if the external air temperature (the temperature of wind blown to the exterior condenser 1210) is 30xc2x0 C., then while the saturation temperature of the refrigerant flowing through the exterior condenser 1201 and the interior condenser 1202 is 50xc2x0 C., only a subcooling degree of the temperature of 20xc2x0 C. or so can be obtained even if the refrigerant is cooled ideally to 30xc2x0 C. of the external air temperature.
Accordingly, where the biasing force of the regulating spring 1104 of the subcooling control valve 1100 is set in the subcooling cycles shown in FIGS. 101 and 102 so that the subcooling degree of 20xc2x0 C. may be obtained at the interior condenser 1202, the subcooling control valve 1100 tends to control the subcooling degree of 20xc2x0 C. even when cool wind of the temperature of 0xc2x0 C. or around it cooled by the interior evaporator 1203 is blown to the interior condenser 1202. Consequently, a sufficiently high subcooling degree (50xc2x0 C.) cannot be obtained making use of cool wind of the temperature of 0xc2x0 C. or around it as described hereinabove.
On the contrary, where the biasing force of the regulating spring 1104 of the subcooling control valve 1100 is set so that the subcooling degree of 50xc2x0 C. may be obtained at the interior condenser 1202, even when the temperature of draft air blown to the interior condenser 1202 in the refrigerating cycle shown in FIG. 101 is 30xc2x0 C. or around it or even when the air mixing damper 1211 in the refrigerating cycle shown in FIG. 102 closes the interior condenser 1202, the subcooling control valve 1100 tends to reduce the opening of the throttle section 1102 until the subcooling degree of 50xc2x0 C. is obtained at the interior condenser 1202, and consequently, the pressure on the high pressure side rises to a very high level.
In the conventional subcooling control valve 1100, the biasing force of the regulating spring 1104 is set so that a predetermined subcooling degree may be obtained in the interior condenser 1202 in this manner. Accordingly, the conventional subcooling control valve 1100 cannot cope with the construction of such a cycle wherein the temperature of air blown to the interior condenser 1202 varies over a wide range so that subcooling obtained at the interior condenser 1202 varies over a wide range (the subcooling degree cannot be controlled over a wide range), and consequently, the cycle efficiency is low.
It is an object of the present invention to provide an automotive air conditioner for an automobile, which has an engine of the type wherein engine cooling water does not make a sufficient heat source or has no surplus heat source such as an electric automobile, wherein desirable air conditioning can be performed making full use of a variation of heat involved in condensation and evaporation in a refrigerating cycle.
It is another object of the present wherein the capacity of a compressor can be variably controlled by driving the compressor by means of an electric motor and air conditioning can be performed efficiently with a low power by suitably controlling the discharging capacity of the compressor and re-heating of air by means of a heater.
It is a still further object of the present invention to provide an automotive air conditioner wherein cooling operation or heating operation can be performed efficiently by controlling a flow of refrigerant to an outside heat exchanger which is provided to complement the capacities of a heater and an evaporator disposed in a duct.
It is a yet further object of the present invention to provide an automotive air conditioner wherein cooling operation, dehumidifying operation and heating operation can be achieved by suitably controlling a flow of refrigerant discharged from a compressor between an evaporator and a heater disposed in a duct and an outside heat exchanger disposed outside the duct.
It is a yet further object of the present invention to provide an automotive air conditioner wherein cooling operation, dehumidifying operation and heating operation can be achieved better by varying the heat exchanging capacities of an outside condenser and an outside evaporator provided to complement the condensing and evaporating functions of a heater and an evaporator.
It is a yet further object of the present invention to provide an automotive air conditioner wherein the operation thereof can be changed over between heating operation in which refrigerant circulates in the order of a compressor, a heater, decompressing means and an outside heat exchanger and dehumidifying operation in which the refrigerant flows in the order of the compressor, the heater, the outside heat exchanger, the decompressing means and an evaporator by changing over the flow of the refrigerant and heating operation can be maintained while preventing fogging up of the windshield and so forth by changing over the operation suitably to dehumidifying operation when necessary even in a conditoiner of heating operation.
It is a yet further object of the present invention to provide an automotive air conditioner wherein the operation is changed over between a heating operation condition and a dehumidifying operation condition by changing over means and defrosting of an outside heat exchanger can be achieved by changing over, even in a heating operation condition, the operation to a dehumidifying operation condition in a condition wherein it is forecast that the outside heat exchanger may be frosted.
It is a yet further object of the present invention to provide an automotive air conditioner wherein the operation is changed over between a heating operation condition and a dehumidifying operation condition by changing over means and defrosting of an evaporator can be achieved well by changing over, even in dehumidifying operation, the operation to heating operation in a condition wherein it is forecast that the evaporator may be frosted.
It is a yet further object of the present invention to provide an automotive air conditioner wherein the condensing pressure of refrigerant in a heater can be varied to control the temperature of the heater by performing condensing of the refrigerant, in dehumidifying operation, by both of the heater and an outside heat exchanger and varying the condensing capacity of the outside heat exchanger.
It is a yet further object of the present invention to provide an automotive air conditioner wherein the pressure of refrigerant in an evaporator is prevented from dropping below a predetermined value thereby to prevent fogging up of an inside evaporator by providing a flow of refrigerant which bypasses the inside evaporator and changing over, the refrigerant between a flow which flows to the inside evaporator side and another flow which flows to the bypass passageway by means of a solenoid valve.
It is a yet further object of the present invention to provide an automotive air conditioner wherein high pressure side refrigerant in a refrigerating cycle can have a sufficient subcooling degree and efficient operation of the refrigerating cycle can be performed by dividing an inside heater into a plurality of inside heaters and using the inside heater on the upstream side of a refrigerant flow as a condenser which performs condensing of the refrigerant while using the flow as a subcooler which performs radiation of heat of condensed high pressure liquid refrigerant.
It is a yet further object of the present invention to provide an automotive air conditioner wherein the amount of heat to be absorbed upon operation of a heat pump is increased to enhance the heating capacity by using an inside heater as a condenser and using both of an inside evaporator and an outside heat exchanger as evaporators when the heating load is high such as upon starting of heating operation under a low temperature and particularly when heating by inside air circulation is performed.
It is a yet further object of the present invention to provide an automatic air conditioner wherein an inside heater is divided into an inside condenser and an inside subcooler and throttling amount control of expanding means can be performed appropriately even in a condition wherein refrigerant does not substantially flow into either of the inside condenser and the inside subcooler in a cycle in which the throttling amount of the expanding means is varied so that a predetermined subcooling amount may be obtained with the inside subcooler.
It is a yet further object of the present invention to provide an automatic air conditioner wherein a receiver for suitably absorbing a variation of a flow rate of refrigerant which circulates in a refrigerating cycle can be installed well in the refrigerating cycle.
It is an additional object of the present invention to provide an automatic air conditioner wherein, even in case frost is detected on a surface of an evaporator when dehumidifying operation is to be performed, defogging of the evaporator can be performed without involving a great variation of the temperature of air to be blasted.
In order to attain the objects, according to the present invention, the construction is employed wherein an evaporator and a heater which constitute a refrigerating cycle are disposed in a duct which defines an air passageway.
Further, according to the present invention, a bypass passageway is formed sidewardly of a heater in a duct, and the amount of air to pass the bypass passageway and the amount of air to pass the heater are variably controlled continuously using an air mixing damper.
Further, according to the present invention, the cooling capacity of an evaporator in a duct and the heating capacity of a heater in the duct are suitably controlled by suitably controlling a flow and a flow rate of refrigerant to flow into the heater and the evaporator in the duct and also into an outside heat exchanger outside the duct.
Further, according to the present invention, a compressor is driven by an electric motor, and the speed of rotation of the electric motor is continuously controlled by a controller to variably control the discharging capacity of a compressor.
Further, according to the present invention, an outside heat exchanger is disposed outside a duct so that the heat exchanging performance of a heater or an evaporator may be complemented by the outside heat exchanger.
Further, according to the present invention, changing over means is disposed so that a flow of refrigerant passing an outside heat exchanger may be changed over in response to an operation condition required for the automotive air conditioner, that is, a heating operation condition or a cooling operation condition. Further, according to the present invention, an outside heat exchanger is divided into an outside condenser used only for condensation and an outside evaporator used only for evaporation and varying means are provided for varying the condensing function of the outside condenser and the evaporating function of the outside evaporator.
Further, according to the present invention, changing over means is provided so as to effect changing over control among a cooling operation condition wherein refrigerant circulates in the order of a compressor, an outside heat exchanger, decompressing means and an evaporator, a heating operation condition wherein refrigerant circulates in the order of the compressor, the heater, the decompressing means and the outside heat exchanger and a dehumidifying operation condition wherein refrigerant circulates in the order of the compressor, the heater, the outside heat exchanger, the decompressing means and the evaporator.
Further, according to the present invention, in a condition wherein it is forecast that the windshield of a room of an automobile is fogged, changing over means is controlled to be driven to change over the dehumidifying operation condition.
Further, according to the present invention, in a condition wherein freezing of an evaporator is forecast, changing over means is controlled to be driven to change over the operation from a dehumidifying operation condition to a heating operation condition.
Further, according to the present invention, means is provided for changing over, in a condition wherein freezing of an outside heat exchanger is forecast, refrigerant to be admitted into an outside heat exchanger from a low pressure condition after passing expanding means to a high pressure condition before passing the expanding condition.
Further, according to the present invention, means for varying the capacity of an outside heat exchanger is provided, and upon dehumidifying operation in which both of the outside heat exchanger and a heater perform condensation of refrigerant, the capacity of the outside heat exchanger is varied to vary the condensing temperature of the heater.
Further, according to the present invention, a bypass passageway for flowing refrigerant bypassing an inside evaporator is provided, and a flow of refrigerant is controlled to be changed over by a solenoid valve between a flow which flows to the inside evaporator side and another flow which flows to the bypass passageway side.
Further, according to the present invention, an inside heater is divided into a plurality of inside heaters, and the inside heater on the upstream side in a flow of refrigerant operates as an inside condenser while the inside heater on the downstream side in a flow of refrigerant functions as an inside subcooler.
Further, according to the present invention, an inner heater functions as a condenser while an outside heat exchanger functions as an evaporator upon heating operation, and when the heating load is particularly high, changing over of a flow of refrigerant is controlled so that also the inside evaporator operates as an evaporator together with the outside heat exchanger.
Further, according to the present invention, such a construction is employed that an inside heater is divided into an inside condenser and an inside throttling amount of an expansion valve is controlled so that a predetermined subcooling degree can be obtained, and refrigerant flows into the inside subcooler upon heating operation and upon dehumidifying operation.
Further, according to the present invention, such a construction is employed that a refrigerating cycle wherein a receiver is disposed on the upstream side of expanding means in a flow of refrigerant is formed and the location of the receiver is always positioned on the upstream side of the expanding means even if the operation is changed over to any of cooling operation, heating operation or dehumidifying operation.
Further, according to the present invention, an automotive air conditioner adopts such a construction that, when a frosted condition of an evaporator is forecast or detected upon dehumidifying operation wherein a heat exchanger on the upstream side in a duct functions as a refrigerant evaporator and another heat exchanger on the downstream side in the duct functions as a refrigerant condenser, the condition of an outside heat exchanger is changed over between a condition wherein it is not used as a heat exchanger between refrigerant and air or it is used as a refrigerant condenser to another condition wherein it is used as a refrigerant evaporator. Because the construction described above is employed, with the automotive air conditioner, the evaporator disposed in the duct only performs cooling of air while the heater disposed in the duct only performs heating of air. Accordingly, such a situation is eliminated that a single heat exchanger alternatively performs cooling of air or heating of air in accordance with an operation condition. Besides, since cooling of air by the evaporator and heating of air by the heater are used in combination, appropriate temperature control can be achieved while performing dehumidification of air.
Further, with the automotive air conditioner, the cooling capacity can be varied to vary the temperature of air after passing the evaporator by variably controlling the discharging capacity of the compressor.
Further, with the automotive air conditioner, while outside heat exchanger is disposed outside air and refrigerant, the heat exchanging function of the heater or the evaporator by changing over a flow of refrigerant to flow to the outside heat exchanger between a flow of refrigerant to flow to the heater and a returning flow of refrigerant from the evaporator. In this instance, the outside heat exchanger has a function as a condenser or a function of an evaporator by changing over the flow of refrigerant. However, since the outside heat exchanger performs heat exchanging between air outside the duct and refrigerant, even if moisture is produced by a large amount at some location upon changing over operation, this will not make an obstacle to driving of the automobile or the like.
Further, with the automotive air conditioner, since the bypass passageways are provided sidewardly of the evaporator and the heater and the ratio of a flow rate of air flowing through either one of the bypass passageways to another flow rate of air flowing through the evaporator or the heater is controlled by the damper, cooling of air and heating of air in the duct can be controlled. As a result, useless cooling and useless re-heating of air can be eliminated.
Further, with the automotive air conditioner, since the outside heat exchanger is divided into the outside condenser and the outside evaporator installed separately, also the outside heat exchanger is always specified in function, and the outside condenser and the outside evaporator are installed at optimum locations in accordance with respective functions.
Further, in this instance, since the varying means is employed for varying the heat exchanging functions of the outside condenser and the outside evaporator, the functions of the condenser and the evaporator installed in the duct can be variably controlled in connection with the functions of the outside condenser and the outside evaporator.
Further, with the automotive air conditioner, since the bypass passage for flowing refrigerant bypassing the evaporator is provided and a flow of refrigerant is controlled to be changed over between the evaporator side and the bypass passageway side, when the pressure of refrigerant in the evaporator becomes lower than a predetermined value, refrigerant can be flowed to the bypass passageway side. Since refrigerant does not flow through the evaporator when refrigerant flows to the bypass passageway side, the result. Then, when the pressure of refrigerant in the evaporator rises higher than the predetermined value, refrigerant is changed over so that it may be flowed to the evaporator side again. The pressure of refrigerant in the evaporator can be controlled to the predetermined value by performing such changing over as described just above.
Further, with the automotive air conditioner, since the inside heater is formed separately as a heat exchanger which functions as a condenser and another heat exchanger which functions as a subcooler for subcooling condensed liquid registrant, refrigerant on the high pressure side in the refrigerating cycle can have a sufficiently high subcooling degree, and efficient operation of the refrigerating cycle can be performed.
Further, with the automotive air conditioner, upon heating operation, radiation of heat is performed by the inside heater while the inside heat exchanger serves as an evaporator in which absorption of heat is performed, and when the heating load is particularly high such as upon starting of heating in a low temperature condition, refrigerant passes also through the evaporator so that absorption of heat may be performed also in the evaporator. The heating capacity can be enhanced by increasing the amount of heat absorption in this manner.
Further, with the automotive air conditioner, the inside heater is divided into the condenser and the subcooler, and a temperature sensing tube is provided for varying the throttling amount of the expanding means so that the subcooling degree of refrigerant on the exit side of the inside condenser may be substantially constant in order that refrigerant passing the subcooler may have a predetermined subcooling degree. In the refrigerating cycle having such a construction as described just above, even in a condition wherein no refrigerant flows into the inside condenser and the inside subcooler, operation of the refrigerating cycle can be performed with certainty by employing a fixed throttle in addition to throttling for the expanding means provided by the temperature sensing tube.
Further, with the automotive air conditioner, since, upon dehumidifying operation, the heat exchanger on the upstream side in the duct functions as a refrigerant evaporator and the heat exchanger on the downstream side in the duct functions as a refrigerant upstream side, it is cooled, whereupon saturated vapor is removed from the air, whereafter it is heated when it passes through the heater on the downstream side, and after then, it is blasted into the room of the automobile. Then, if the temperature of the evaporator drops to a temperature at which frosting occurs or to a temperature near to such temperature at which frosting occurs, the controlling apparatus detects or forecasts such frosting by means of the frost sensor. Then, the controlling apparatus controls the flow passage changing over means to change over the outside heat exchanger from a condition wherein the outside heat exchanger is not used as a heat exchanger between refrigerant and air or is used as a refrigerant condenser to another condition wherein the outside heat exchanger is used as a refrigerant evaporator.
Then, since the evaporator and the outside heat exchanger both function as refrigerant evaporators, the evaporating pressure is raised, and frosting of the heat exchanger on the upstream side is prevented.
It is an object of the present invention to provide a refrigerating cycle by which an optimal subcooling degree to assure a high cycle efficiency can be obtained even when the subcooling degree obtained is varied over a wide range by a variation of temperature of refrigerant blown to a refrigerant condenser.
In order to attain the object described above, according to the present invention, there is provided a refrigerating cycle, which comprise a refrigerant condenser having a heat exchanging section for condensing refrigerant passing therethrough into liquid by heat exchange with a cooling medium, at least a lower stream area portion of the heat exchanging section being disposed in a temperature field in which the temperature of the cooling medium varies over a wide range, and a subcooling control valve including a throttle section for throttling a refrigerant flow passageway on the downstream of the refrigerant condenser, a valve member for opening and closing the throttle section, and a temperature sensitive section for converting a variation of temperature of the refrigerant on the upstream of the lower stream area portion into a variation of pressure, the valve member being displaced to adjust the opening of the throttle portion in accordance with the pressure variation of the temperature sensitive section so that the subcooling degree on the upstream of the lower stream area portion may be a predetermined value.
Preferably, the refrigerant condenser includes a mounting pipe for mounting the temperature sensitive section thereon, and the mounting pipe is provided such that it projects sidewardly of the head exchanging section on the upstream of the lower stream area portion.
In the refrigerating cycle, the opening of the throttle section of the subcooling control valve is adjusted so that the subcooling degree on the upstream in the downstream area of the refrigerant condenser may be the predetermined value.
Accordingly, the refrigerant flowing into the lower stream area portion of the refrigerant condenser is in the form of liquid refrigerant cooled already to the subcooling degree of the predetermined value. Consequently, a maximum subcooling degree which can be obtained in the lower stream area portion can be obtained in response to a variation of temperature of the cooling medium which exchanges heat with the refrigerant in the lower stream area section. In short, even if the temperature of the cooling medium which exchanges heat with the refrigerant in the lower stream area portion varies over a wide range, a subcooling degree corresponding to a temperature difference between the temperature of the cooling medium and the saturation temperature of the refrigerant on the upstream of the lower stream area portion (temperature of the cooling medium saturation temperature of the refrigerant) can be obtained.
The above and other objects, features and advantages of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings in which like parts or elements are denoted by like reference characters.